This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).

Natural mycoflora and co-occurrence of fumonisins (FB1, FB2) and aflatoxins (AFB1, AFB2, AFG1 and AFG2) in freshly harvested corn grain samples from four regions of Brazil were investigated. Fusarium verticillioides was predominant in all samples. Analysis of fumonisins showed that 98% of the samples were contaminated with FB1 and 74.5% with FB1 + FB2, with toxin levels ranging from 0.015 to 9.67 μg/g for FB1 and from 0.015 to 3.16 μg/g for FB2. Twenty-one (10.5%) samples were contaminated with AFB1, seven (3.5%) with AFB2 and only one (0.5%) with AFG1 and AFG2 Co-contamination with aflatoxins and fumonisins was observed in 7% of the samples. The highest contamination of fumonisins and aflatoxins was observed in Nova Odessa (SP) and Várzea Grande (MT), respectively. The lowest contamination of these mycotoxins was found in Várzea Grande and Nova Odessa, respectively.

Corn (Zea mays L.) is grown in hot and temperate regions around the world and is the second most cultivated crop in Brazil. The country is currently the world’s third largest producer after the United States and China, with an average production of about 43 million tons over the last five years [1]. Since corn grain posses a high nutritional value, it is used for the preparation of diverse food products, and represents a relevant and important socioeconomic factor in many regions of the world [2].

Corn can be affected by different toxigenic fungi, especially Fusarium verticillioides (Sacc.) Nirenberg (=F. moniliforme Sheldon) and F. proliferatum (Matsushima) Nirenberg and Aspergillus flavus Link, the main producers of fumonisins and aflatoxins, respectively. Contamination with these toxins is one of the main factors compromising the quality of corn products [3].

Twenty-eight fumonisin analogs have been described so far, with fumonisin B1 (FB1) being the most important of the group due to its abundance in corn grain and because it is the most toxic among the fumonisin isomers [4]. FB1 has been shown to be hepatotoxic to all animals species studied so far [5–9]. In addition, FB1 is known to cause leukoencephalomalacia in horses [6] and pulmonary edema and hydrothorax in swine, and to exert nephrotoxic as well as hepatotoxic activity in rats [8] and rabbits [10–12]. In humans, FB1 has been associated with esophageal cancer [4]. On the basis of toxicological evidence, the International Agency for Research on Cancer (IARC) has established that FB1 is potentially carcinogenic (class 2B) to humans [13].

Aflatoxins are secondary metabolites produced by toxigenic strains of A. flavus and A. parasiticus. Chemically, aflatoxins belong to the bifuranocoumarin group, with aflatoxins B1 (AFB1), B2 (AFB2), G1 (AFG1) and G2 (AFG2) being the most toxic. Liver is the main organ affected by these toxins. In addition to its hepatotoxic action, AFB1 is also highly mutagenic, carcinogenic and probably teratogenic to animals. The IARC classifies AFB1 within class 1 of human carcinogens [14].

In Brazil, the presence of aflatoxins in corn is regulated by the Ministry of Agriculture through Decree 183 of March 21, 1996 and Resolution 274 of October 15, 2002 of the National Sanitary Surveillance Agency, which establish a maximum limit of 20 μg/kg for the sum of aflatoxins B1, B2,G1 and G2 [15,16]. No limit has been established yet in Brazil for fumonisins in foods. However, the countries of European Union recommend a limit of 2,000 μg/kg for the sum of FB1 and FB2 in unprocessed corn [17]. In addition, Food and Drug Administration (FDA) recommends levels of 2 to 4 ppm for products intended for human consumption and of 5 to 100 ppm for products destined for animal feeding [18].

Occurrence of fumonisins and aflatoxins in corn and corn products has been a world-wide problem. In view of the difficulty in removing these mycotoxins, monitoring of grains during the period from planting to harvest is important for the control of exposure to these toxins [19]. Therefore, the objective of the present study was to evaluate the occurrence of fungi and the incidence of fumonisins and aflatoxins in corn grains freshly harvested in four regions in Brazil.

2.Experimental Section2.1.Corn samples

A total of 200 corn samples (Agromen 2012 hybrid, AGN 2012) freshly harvested from the following four different regions of Brazil were analyzed: Várzea Grande (Mato Grosso, MT); Nova Odessa (São Paulo, SP); Santa Maria (Rio Grande do Sul, RS), and Oliveira do Campinhos (Recôncavo Bahiano, Bahia, BA). The study regions are characterized by variations in climatic conditions during the period from sowing to harvest (Table 1). Samples (50 per region) were sown in November 2004 and harvested in April 2005. Sampling was performed according to the method proposed by Delp et al. [20]. The area selected for sowing in each region was divided into 10 parcels of 80 m2 each. Five parcels were chosen from each area, and 10 ears of corn were sampled from each parcel. In this way, five samples were collected at each region, containing 10 ears of corn. A 1 kg subsample was taken from each of these samples and assayed for mycoflora, aflatoxin and fumonisins contents, and water activity (aw).

Approximately 30 g of grains were obtained from each corn subsample (1 kg) and disinfected with 0.4% sodium hypochlorite solution for 2 min, followed by washing with sterile distilled water for elimination of external contaminants. After disinfection, some grains were randomly separated and directly seeded into Petri dishes containing Dichloran Rose Bengal Chloramphenicol agar (DRBC). Three plates containing 11 grains were used for each sample. The plates were incubated at 25 °C for five days and the results were expressed as the percentage of total grains infected with fungi [21].

Fungal colonies were identified to the genus level and those belonging to the genera Fusarium and Aspergillus were identified to the species level according to Raper and Fennell [22], Pitt and Hocking [23], Nelson et al. [24] and Leslie and Summerell [25].

2.4.Determination of fumonisins

Twenty grams of each previously triturated sample was transferred to a 250 mL centrifuge bottle and 50 mL of a mixture of acetonitrile-methanol-water (25:25:50, v/v/v) was added. After shaking for 20 min in a horizontal mechanical shaker, the samples were centrifuged at 2,500 × g for 10 min and the supernatant was filtered through Whatman No. 4 filter paper (12 cm). The steps were repeated for the precipitate and the filtrates were collected. Ten milliliter was combined with 40 mL phosphate buffer saline (PBS), pH 7.0 (8.0 g NaCl, 1.2 g anhydrous Na2HPO4, 0.2 g KH2PO4, 0.2 g KCl in approximately 990 mL water, pH was adjusted with 2M HCl, and diluted to 1 L) and the mixture was shaken. Diluted extracts were filtered through microfiber filter paper (Whatman GF/A, 9 cm) and 10 mL was collected for purification on an immunoaffinity column (FumoniTest - Vicam) at a flow rate of 1–2 drops/s. The column was washed with 10 mL PBS (pH 7.0) at 1–2 drops/s for removal of residues. Fumonisins were eluted with 1.5 mL methanol (HPLC grade) at 1 drop/s, evaporated to residue in a water bath, and submitted to detection and quantification [26].

Fumonisins were quantified based on a calibration curve using standard solutions of FB1 and FB2. Concentrations of standard solutions ranging from 0.025 to 2000 ng/μL for FB1 and from 0.0125 to 1000 ng/μL for FB2 were used. Coefficient of correlation was 0.99277 for FB1 and 0.995047 for FB2.

Quantification limit for FB1 was 0.015 μg/g, with a mean recovery of 92.38% and standard deviation of 13.68% (five replicates). For FB2, quantification limit was 0.015 μg/g, with a mean recovery of 85.39% (five replicates, standard deviation: 6.87%).

2.5.Determination of aflatoxins

Aflatoxins B1 and B2 were determined according to the method described by Soares and Rodriguez-Amaya [27]. Briefly, 50 g of each sample of grains was extracted with 270 mL methanol and 30 mL 4% potassium chloride. Samples were blended at moderate speed for 30 min and filtered, and 150 mL of the filtrate was collected into a graduated cylinder. Next, 150 mL 30% ammonium sulfate solution and 50 mL diatomaceous earth were added. The suspension was filtered through filter paper and a 150-mL aliquot was transferred to a separation funnel containing 150 mL distilled water. The toxins were extracted three times with 10 mL chloroform. The chloroform extracts were collected in a beaker and the solvent was evaporated in a water bath at 60 °C.

The dried extracts were resuspended in 500 μL chloroform and immediately subjected to thin-layer chromatography. Final identification and quantification of aflatoxins were performed by one-dimensional thin-layer chromatography on precoated silica gel plates G-60 (Merck). The plates were developed in a saturated chamber with chloroform-acetone (9:1, v/v). The fluorescent spots corresponding to AFB1 and AFB2 were observed in a dark chamber under ultraviolet light (λ = 366 nm). Aflatoxins were determined by visual comparison with AFB1 and AFB2 standards prepared. Confirmatory tests were carried out using trifluoroacetic acid [28]. The quantification limit of the method was 2 μg/kg for AFB1, with a mean recovery of 91.99% and standard deviation of 6.93% (five replicates), and 4 μg/kg for AFB2, with a mean recovery of 92% and standard deviation of 13.32% (five replicates).

2.6.Statistical analysis

Results were analyzed statistically using the Gamlss R 2.8.1 package and Statistical Analysis Software (SAS) version 8.0. Spearman’s correlation coefficient was used to analyze fungal growth in the grains. Gamlss model (5% level of significance) was used to determine the effect of different regions studied and water activity on fungal growth, as well as the effect of the different regions on incidence of mycotoxins [29]. Gamlss model (5% level of significance) was also used to evaluate the effect of different regions and fungal growth on incidence of mycotoxins. Bonferroni’s test was used for multiple comparisons between regions [30]. Low frequency of contamination with AFB2, AFG1 and AFG2 did not permit model fit for inferential analysis of these toxins.

3.Results and Discussion

The results regarding the mycoflora detected in corn grain samples obtained from four different regions (São Paulo, Mato Grosso, Rio Grande do Sul and Bahia) are shown in Table 2. Fungal contamination was observed in 100% of the corn samples analyzed, with Fusarium verticillioides being the most frequent species in all regions.

The following species and genera were isolated from the 50 corn grain samples collected in Nova Odessa-SP: Fusarium verticillioides (88.6%), F. proliferatum (7.6%), Penicillium (15.4%), Cladosporium (10.4%), Trichoderma (1.1%), and Mucor (0.1%). Aw values ranged from 0.78 to 0.89, with a mean of 0.87.

Spearman’s correlation test revealed a moderately high, negative correlation (r = −0.61; p < 0.0001) between isolation of genera Fusarium and Aspergillus, suggesting that samples with a high percentage of Fusarium contamination tend to have low contamination with Aspergillus.

Inferential analysis of the growth of Fusarium was performed using the Gamlss model with beta inflated distribution [29]. Results showed that frequency of Fusarium in corn grains varied as function of aw and of the different regions studied (p < 0.0001).

The same model was used for analysis of growth of Aspergillus, but frequency of Fusarium was included as a predictive variable. Aspergillus growth varied as function of growth of Fusarium (p = 0.0002), as well as function of aw and region (p < 0.0001).

According to Lillehoj et al. [31] and Deacon [32], F. verticillioides is a strong competitor of A. flavus. These fungi present a passive antagonistic relationship in which growth is inhibited by competition for space or essential nutrients, with advantages for microorganisms that are present in larger number or are better adapted to the substrate. Marín et al. [33], studying the influence of water activity and temperature on interaction between filamentous fungi, observed that F. verticillioides strains became more competitive and were able to inhibit other fungal genera such as Aspergillus and Penicillium when maintained on a substrate with a high aw at a temperature of 15 °C.

However, according to Cuero et al. [34], there is no indication of antagonism with A. flavus or of any effect on the levels of aflatoxin in maize grains. There could be a synergism between these two species, therefore, F. verticillioides can stimulate the metabolism of A. flavus and increase aflatoxin production. In the present study, growth of Fusarium spp. was probably favored in the region where mean aw levels were around 0.87 (Nova Odessa-SP). On the other hand, the lowest aw (0.76) observed in Várzea Grande-MT resulted in a higher frequency of isolation of Aspergillus spp. (14%) and a lower frequency of Fusarium spp. (84.2%) (Table 2).

Fumonisins were the most frequent mycotoxins in 200 samples analyzed. This result agrees with those obtained by mycological analysis demonstrating that F. verticillioides was the predominant species. Contamination with FB1 was observed in 98% of freshly harvested corn analyzed (196 samples) and contamination with FB1 + FB2 in 74.5% (149 samples). Frequency of contamination and concentrations of FB1 and FB2 are shown in Table 3.

Our results showed that 57.7% (86 samples) of the 149 samples contaminated with FB1 + FB2 had levels higher than those recommended by the European Union [17] (2 μg/g) and 28.9% (43 samples) had levels higher than 4 μg/g, the maximum level recommended by the FDA [18] for products intended for human consumption.

Highest levels of fumonisin contamination were observed in Nova Odessa-SP, with FB1 concentrations ranging from 0.091 to 9.67 μg/g (mean: 2.81 μg/g) and FB2 concentrations from 0.017 to 3.06 μg/g (mean: 0.95 μg/g). In this region, the meteorological data (mean temperature: 24.6 °C; relative humidity: 79.3% and rainfall index: 6 mm) might have favored the production of these toxins.

According to Hennigen et al. [35], elevated fumonisin levels in corn are associated with high relative air humidity. Gong et al. [36] reported that temperature, relative humidity and rainfall were responsible for high levels of contamination of corn grains with FB1 in China. According to FDA [18], these meteorological parameters in different geographic regions during pre-harvest and harvest periods were found to highly influence on fumonisin levels in corn.

In Brazil, studies of the occurrence of FB1 and FB2 in freshly harvested corn have revealed detection rates of 92.3% and 81%, respectively. Most of these samples collected in different regions contained levels ranging from 0.02 to 78.92 μg/g for FB1 (mean: 4.9 μg/g) and from 0.02 to 29.16 μg/g for FB2 (mean: 3.9 μg/g) [19,37–47]. In the present study, presence of FB1 ranged from 92% to 100%, toxin levels from 0.015 to 9.67 μg/g, and mean concentration from 0.72 to 2.81 μg/g. Presence of FB2 ranged from 50% to 98%, toxin levels from 0.02 to 3.16 μg/g and mean concentration from 0.15 to 0.95 μg/g (Table 3). It should be emphasized that this is the first report of occurrence of fumonisins in corn from Bahia and the first comparative study between corn-producing regions in Brazil.

Gamlss model with a gamma distribution was used for statistical analysis of FB1 since samples had a low probability of being equal to zero [49]. Mean contamination of grain with FB1 varied as function of region (p < 0.0001) and growth of Fusarium (p = 0.0009). Since contamination with FB2 assumed values ≥ 0, with a high probability of being equal to zero, Gamlss model with a zero adjusted inverse Gaussian distribution was used for analysis [48]. Probability of fumonisin level being greater than or equal to 0 is 100% since contamination level cannot be a negative value (p < 0.0001 and p = 0.0206, respectively) and it varied according to region. Using these models, the average probability of contamination of corn grains with FB1 and FB2 was higher in Nova Odessa-SP and Oliveira dos Campinhos-BA than in Várzea Grande-MT and Santa Maria-RS.

Among 200 samples analyzed, 21 (10.5%) were contaminated with AFB1, seven (3.5%) with AFB2 (Table 4) and only one (0.5%) with AFG1 and AFG2. Sixteen (76.2%) of 21 positive samples had total aflatoxins concentration (B1 + B2 + G1 + G2) higher than the limit established by Brazilian regulations (20 μg/kg) [15,16].

In Nova Odessa (SP), only one sample (2%) was contaminated with AFB1 at a concentration of 34.2 μg/kg (mean: 0.68 μg/kg). This finding might be explained by the absence of A. flavus in corn collected in this region. Pozzi et al. [50], analyzing 130 corn samples from Ribeirão Preto, SP, also reported low contamination with AFB1. Almeida et al. [42], investigating the occurrence of aflatoxins in corn from Capão Bonito and Ribeirão Preto, did not observe contamination with this toxin in any of the 57 samples. According to Salay and Mercadante [51], percentage of contamination of corn and derivatives with aflatoxins in the State of São Paulo (11.5%) is lower than that observed in North (32.9%), South (33.4%) and Northeast (96.9%) regions of Brazil.

In Santa Maria (RS), seven (14%) samples were contaminated with AFB1 and five (10%) with AFB2 at levels ranging from 13.7 to 1,393 μg/kg (mean: 50.5 μg/kg) and from 5.6 to 55.7 μg/kg (mean: 3.5 μg/kg), respectively. One sample was contaminated with AFG1 (39.2 μg/kg, mean: 0.78 μg/kg) and AFG2 (29.7 μg/kg, mean: 0.59 μg/kg). In Várzea Grande (MT), nine (18%) samples were contaminated with AFB1 and two (4%) with AFB2 at levels ranging from 6.8 to 976.1 μg/kg (mean: 27.7 μg/kg) and from 22.3 to 33.4 μg/kg (mean: 1.11 μg/kg), respectively. Among samples collected in Oliveira dos Campinhos (BA), four (8%) were contaminated with AFB1 at levels ranging from 13.7 to 47.8 μg/kg (mean: 2.05 μg/kg). Aflatoxin B2 was not detected in samples from this region.

Gamlss model with a zero-adjusted Gaussian distribution was used for inferential analysis of AFB1 contamination. The probability of AFB1 contamination being greater than or equal to 0 is 100%, since contamination level cannot be less than 0 (p = 0.0030 and p = 0.0006, respectively) and it varied only as a function of frequency of A. flavus.Thus, the higher the fungus frequency, the higher the probability of contamination of corn with AFB1.

Some Brazilian studies have reported occurrence of aflatoxins in corn grains. In these studies, the frequency of positive samples ranged from 11.3% to 77.1% (mean: 30.6%), with toxin levels ranging from 1 to 1906 μg/kg [41,43,52–56]. In the present investigation, the frequency of positive samples for AFB1 and AFB2 ranged from 2% to 18%, and toxin levels ranged from 5.6 to 1393 μg/kg (mean: 2.05 to 50.5 μg/kg) (Table 4).

According to Lacey et al. [57], temperatures and aw for growth of A. flavus range from 6 °C to 45 °C and from 0.78 to 0.80, respectively. Marín et al. [33] demonstrated that Aspergillus species are more competitive at high temperatures, with optimum growth rate for A. niger and A. flavus ranging from 30 °C to 37 °C. Zorzete et al. [58], analyzing the distribution of aflatoxins and fumonisins in corn kernels inoculated with A. flavus and F. verticillioides from flowering to harvest, observed that A. flavus was better adapted to high temperature and low humidity, with the demonstration of a significant negative linear correlation between fungal frequency and rainfall.

4.Conclusions

In the present study, better adaptation of F. verticillioides to the temperature water activity levels, contributed to high frequency of isolation of this species and lower incidence of A. flavus in corn samples collected from diverse locations in Brazil. Only 7% of 200 corn samples collected in four regions were contaminated with both aflatoxins and fumonisins. However, frequency of samples testing positive for fumonisins as well as high frequency of isolation of Fusarium spp., demonstrate the need for effective prevention and control strategies in order to reduce risks to human and animal health.

The authors thank the Instituto Nacional de Metereologia (INMET) for providing the climatic data of the regions studied and Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP) for financial support.

References and Notes1.Companhia Nacional de Abastecimento (CONAB)Avaliação da safra 2007/2008http://www.conab.gov.br/conabweb/index.php/, accessed November 12, 2008.2.PedrosaAVBDezenRBO milho: Características do mercado e perspectivasPreços Agric199155143.AlmeidaAPSabinoMFonsecaHCorrêaBMilho recém-colhido no Brasil: interação da microbiota fúngica, fatores abióticos e ocorrência de micotoxinas. Rev. Inst.Adolfo Lutz200564194.RheederJPMarasasWFOThielPGFusarium moniliforme and fumonisins in corn in relation to human esophageal cancer in TranskeiPhytopathology1992822532575.JaskiewicsKVan RenaburgSJMarasasWFOGelderblomWCACarcinogenicity of Fusarium moniliforme culture material in ratsJ. Natl. Cancer Inst1987783213256.KellermanTSMarasasWFOThielPGGelderblomWCACawoodMCoetzerJALeukoencephalomalacia in two horses induced by oral dosing of fumonisin B1Onderstepoort J. Vet1990572692757.LedouxDRBrownTPWeibkingTSRottinghausGEFumonisin toxicity in broiler chicksJ. Vet. Diagn. Invest199243303338.VossKAChamberlainWSBaconCWSubchronic feeding study of the mycotoxin fumonisin B1Nat. Toxins199312222289.DilkinPZorzetePMallmanCAGomesJDFUtiyamaCEOettingLLCorrêaBToxicological effects of chronic low doses of aflatoxin B1 and fumonisin B1 containing Fusarium moniliforme culture material in weaned pigletsFood Chem. Toxicol2003411345135310.BucciTJHansenDKLaBordeJBLeukoencephalomalacia and hemorrhage in the brain of rabbits gavaged with mycotoxin fumonisin B1Nat. Toxins19964515211.BucciTJHowardPCTollesonWHLaBordeJBHansenDKRenal effects of fumonisin mycotoxins in animalsToxicol. Pathol19982616016412.GumprechtLAMarcucciAWeigelRMVesonderRFRileyRTShowkerJLShowkerVLBeasleyVRHaschenkWMEffects of intravenous fumonisin B1 in rabbits: Nephrotoxicity and sphingolipid alterationsNat. Toxins1995339540313.International Agency for Research on CancerToxins derived from Fusarium moniliforme: Fumonisin B1 and B2 and Fusarin C (Group 2B)Monographs on the Evaluation of Carcinogenic Risks to HumansIARCLyon, France19935644514.International Agency for Research on CancerAflatoxins: Occurring Aflatoxins (Group 1), Aflatoxin M1 (Group 2B)Monographs on the Evaluation of Carcinogenic Risks to HumansIARCLyon, France19935644515.BRAZIL. Ministry of Agriculture. Decree 183 of March 21, 1996. Art 1. Adopt MERCOSUR Technical Regulation on maximum levels of aflatoxins in milk, peanuts and corn, approved by resolution of the Southern Common Market in 56/94, of 01 January 1995. Published in the Official Gazette of 25 March 1996. http://extranet.agricultura.gov.br/sislegis-consulta/, accessed February 16, 2009.16.BRAZIL. National Sanitary Surveillance Agency. Resolution 274 of October 15, 2002. Approves the Technical Regulation on maximum levels of aflatoxins in milk, peanut and corn. Published in the Official Gazette of 16 October 2002. http://www.anvisa.gov.br/e-legis/, accessed February 16, 2009.17.European Mycotoxin Awareness NetworkEuropean Mycotoxin Awareness Network, a thematic network of 5 Framework Programme R&D call funded by the European Union; EMAN, 2000http://www.mycotoxins.org/, accessed December 19, 2008.18.Food and Drug AdministrationBackground paper in support of fumonisin levels in corn and corn products intended for human consumptionUS Food and Drug Administration, Center for Food Safety and Applied NutritionSilver Spring, Maryland, USA2001http://vm.cfsan.fda.gov/~dms/fumonbg1.html/, accessed February 10, 2009.19.MorenoECGarciaGTOnoMAVizoniEKawamuraOHirookaEYOnoEYSCo-occurrence of mycotoxins in corn samples from the Northern region of Paraná State, BrazilFood Chem200911622022620.DelpRBStewellLJMaroisJJEvaluation of field sampling techniques for estimation of disease incidencePhytopathology1986761299130521.PittJIKingADHockingADDichloran-rose bengal medium for enumeration and isolation of molds from foodsAppl. Environ. Microbiol19793795996422.RaperKBFennellDIThe Genus Aspergillus1st edWilliams & WilkinsBaltimore, MD, USA196568623.PittJIHockingADFungi and Food Spoilage2nd edChapman & HallLondon, UK199759224.NelsonPETousonTAMarasasWFOFusarium Species An Illustrated Manual for IdentificationThe Pennsylvania State University PressUniversity Park, PA, USA198319325.LeslieJFSummerellBAThe Fusarium Laboratory Manual1st edBlackwell PublishingAmes, Iowa, USA200638826.ViscontiASolfrizzoMGirolamoADetermination of fumonisins B1 and B2 in corn and corn flakes by liquid chromatography with immunoaffinity column cleanup: collaborative studyJ. AOAC Int2001841828183727.SoaresLMVRodriguez-AmayaDBSurvey of aflatoxins, ochratoxin A, zearalenone and sterigmatocystin in some Brazilian foods by using multi-toxin thin layer chromatographic methodJ. Assoc. Off. Chem198972222628.ScottPMNatural poisonsAssociation of Official Analytical Chemists. Official Methods of Analysis15th edHelrichKAOACArlington, Virginia, USA19901184121329.RigbyRAStasinopoulosDMGeneralized additive models for location, scale and shapeJ. R. Statist. Soc. C: Appl. Stat20055450755430.NeterJKutnerMKNachtsheimCJWassermanWApplied Linear Statistical Models4th edIrwinChicago, Illinois, USA1996140831.LillehojEBKwolekWFGuthrieWDBarryDMcMillianWWWidstronNWAflatoxin accumulation in preharvest maize (Zea mays L.) kernels, interactions of 3 fungal species in European corn borer Ostrinia nubilis and 2 hybridsPlant Soil1982659510232.DeaconJWIntroduction to Modern Mycology2nd edBlackwell Sci. PublishingLondon, UK19843833.MarínSSanchisVArnauFColonisation and competitiveness of Aspergillus and Penicillium species on maize grain in the presence of Fusarium moniliforme and Fusarium proliferatumInt. J. Food Microbiol19984510711734.CueroRGLillehojEBKwolekWFZuberMSMycoflora and aflatoxin and preharvest maize kernels of varied endosperm typeTrichothecene and Other Mycotoxins1st edLaceyJJohn Wiley & Sons, LtdNew York, NY, USA198510911135.HennigenMRValente SoaresLMSanchezSDi BenedettoNMLonghiAEyherabideGTorrobaJZanelliMFumonisins in corn hybrids grown in Argentina for 2 consecutive seasonsProceedings of the 10th International IUPAC Symposium on Mycotoxins and PhytotoxinsGuaruja, Brazil21–25 May 2000De KoeWJSamsonRAVan EgmondHPGilbertJSabinoMIUPACGuaruja, Brazil200033133936.GongHZJiRLiYXZhangHYLiBZhaoYSunLYuFYangJOccurrence of fumonisin in corn from the main corn - Producing areas of ChinaMycopathologia2009167313637.HirookaEYYamaguchiMMAoyamaSSugiuraYUenoYThe natural occurrence of fumonisins in Brazilian corn kernelsFood Addit. Contam19961317318338.CamargosSMSoaresLMVSawazakiEBolonheziDCastroJLBortolletoNFumonisins in corn cultivars in the State of São PauloBr. J. Microbiol20003122622939.OrsiRBCorrêaBPozziCRSchammassENogueiraJRDiasSMCMalozziMMycoflora and occurrence of fumonisins in freshly harvest and stored hybrid maizeJ. Stor. Prod. Res200036758740.MallmanCASanturioJMDilkinPFumonisin B1 in cereals and feeds from southern BrazilArq. Inst. Biol200168414541.OnoEYSOnoMAFunoFYMedinaAEOliveiraTCRMKawamuraOUenoYHirookaEEvaluation of fumonisin-aflatoxin co-occurrence in Brazilian corn hybrids by ELISAFood Addit. Contam20011871972942.AlmeidaAPFonsecaHFancelliALDireitoGMOrtegaEMCorrêaBMycoflora and fumonisin contamination in Brazilian corn from sowing to harvestJ. Agric. Food Chem2002503877388243.Rodriguez-AmayaDBSabinoMMycotoxin research in Brazil: the last decade in reviewBrazil J. Microbiol20023311144.Van der WesthuizenLShephardGSScusselVMCostaLLFVismerHFRheederJPMarasasWFOFumonisin contamination and Fusarium incidence in corn from Santa Catarina, BrazilJ. Agric. Food Chem2003515574557845.OnoEYSFungaroMHPSofiaSHFigueiraELZGerageACIchioneMSugiuraYUenoYHirookaEYTrends of fumonisin contamination and animal intoxication through monitoring 1991 to 1997 corn crop in the State of Paraná, BrazilMycopathologia200415845145546.HassegawaRHFonsecaHFancelliALSilvaVNSchammassEAReisTACorrêaBInfluence of macro—and micronutrient fertilization on fungal contamination and fumonisin production in corn grainsFood Control200819364347.OnoEYSSilvaMHashimotoEHVizoniEKawamuraOSugiuraYHirookaEYMycotoxicological quality evaluation of corn samples used by processing industries in the Northern region of Paraná State, BrazilFood Addit. Contam2008251848.McCullaghPNelderJAGeneralized Linear Models2nd edChapman and HallLondon, UK198923849.HellerGStasinopoulosMRigbyBThe zero-adjusted inverse Gaussian distribution as a model for insurance claimsProceedings of the 21st International Workshop on Statistical ModellingGalway, Ireland3–7 July, 200622623350.PozziCRCorrêaBGambaleWPaulaCRChacon-RecheNOMeirellesMCAPost-harvest and stored corn in Brazil: Mycoflora interaction, abiotic factors and mycotoxins occurrenceFood Addit. Contam19951231331951.SalayEMercadanteAZMycotoxins in Brazilian corn for animal feed: Occurrence and incentives for the private sector to control the level of contaminationFood Control200213879252.BautistaARPOliveiraMZAMirandaMSSalesLAAflatoxinas em grãos de milho armazenado no Estado da BahiaRev. Soc. Bras. Toxicol19892242553.SabinoMPradoGIonamataIOPedrosoMOGarciaRVNatural occurrence of aflatoxins and zearalenone in maize in BrazilFood Addit. Contam1989632733154.HenningenMRDickTIncidence and abundance of mycotoxins in maize in Rio Grande do Sul, BrazilFood Addit. Contamin19951267768155.GloriaEMFonsecaHSouzaIMOccurrence of mycotoxins in maize delivered to the food industry in BrazilTrop. Sci19973710711056.CôrtesNANetoDCCorrêaBOcorrência de aflatoxinas em milho produzido pelo sistema de cultivo, em comunidades de agricultura familiar, no estado do Mato GrossoRev. Hig. Alim200014162657.LaceyJRamakrishnaNHamerAMaganNMarfleetCGrain fungiHandbook of Applied Mycology: Foods and FeedsBhatnagarDLillehojEBAroraDKMarcel DekkerNew York, NY, USA199212117758.ZorzetePCastroRSPozziCRIsraelALMFonsecaHYanaguibashiGCorrêaBRelative populations and toxin production by Aspergillus flavus and Fusarium verticillioides in artificially inoculated corn at various stages of development under field conditionsJ. Sci. Food. Agric2008884855TablesTable 1.

Meteorological data from sowing to harvest (November, 2004 to March, 2005) of four regions in Brazil.

Location

Mean temperature (°C)

Standard deviation

Mean relative humidity (%)

Standard deviation

Mean rainfall (mm)

Standard deviation

Várzea Grande (MT)

27.1

2.1

40.0

26.4

3.4

6.2

Santa Maria (RS)

22.5

3.5

71.3

11.8

2.8

9.0

Oliveira dos Campinhos (BA)

28.0

1.3

73.7

9.3

6.1

18.0

Nova Odessa (SP)

24.6

2.1

79.3

7.7

6.0

13.4

Table 2.

Mean relative frequency of fungi isolated from 200 corn samples in four regions of Brazil.